The present invention relates generally to the fabrication of integrated circuits on substrates. More particularly, the invention relates to a plasma treatment of carbon-containing layers, such as silicon carbide, to enhance adhesion to an adjacent layer and to minimize oxidation of the carbon-containing layer.
Sub-quarter micron multi-level metallization is one of the key technologies for the next generation of ultra large scale integration (ULSI). Reliable formation of multilevel interconnect features is very important to the success of ULSI and to the continued effort to increase circuit density and quality on individual substrates and die. As circuit density has increased, materials and structural changes have occurred in the substrate stack. Some of the fundamental properties such as layer adhesion and oxidation resistance are needing revisiting as a result.
As layers are deposited in sequence, adhesion between layers becomes important to maintain structural integrity and to meet the performance demands of the devices being formed. The use of new low k materials, useful as barrier layers, etch stops, anti-reflective coatings (ARCs), passivation layers, and other layers must provide good adhesion to be integrated into the fabrication sequence. As an example, some of the new materials for ULSI use halogen doping, such as fluorine, to lower the k value of the layers, while maintaining desirable physical properties, such as strength. However, some of the doped material may outgas in processing. Thus, when adjacent layers are deposited and ultimately annealed, the layers may not properly adhere to each other, resulting in delamination of the layers.
Additionally, the new materials need to have improved oxidation resistance, particularly for layers exposed to an oxidizing plasma. As one example, layers require patterned etching and hence undergo a photolithography process in which a layer of photoresist material (typically organic polymers) is deposited on the layer to define the etch pattern. After etching, the photoresist layer is removed by exposing the photoresist layer to an active oxygen plasma, a process typically referred to as xe2x80x9cashingxe2x80x9d. During the rigorous plasma-enhanced oxidation of the ashing process, the charged particles of the plasma collide with the substrate which can cause film loss and/or distort the crystal lattice of the substrate, thereby comprising the integrity of the devices formed on the substrate. Erosion or film loss can lead to short circuiting between the reduced dimension features such as contacts, vias, lines, and trenches. The oxidation from ashing appears to especially affect carbon-containing materials, such as SiC, and, thus, such materials in general could also benefit from improved adhesion and increased oxidation resistance. Thus, an improved oxidation resistance and film. loss resistance to such rigorous environments is needed to maintain circuit integrity of the reduced dimension features.
Therefore, there is a need for improved processing that increases the resistance to oxidation and adhesion of carbon-containing materials.
The present invention generally provides improved adhesion and oxidation resistance of carbon-containing layers without the need for an additional deposited layer. In one aspect, the invention treats an exposed surface of carbon-containing material, such as SiC, with an inert gas plasma, such as a helium (He), argon (Ar), or other inert gas plasma, or an oxygen-containing plasma such as a nitrous oxide (N2O) plasma. Other carbon-containing materials can include organic polymeric materials, xcex1C, xcex1FC, SiCO:H, and other carbon-containing materials. The plasma treatment is preferably performed in situ following the deposition of the layer to be treated. Preferably, the processing chamber in which in situ deposition and plasma treatment occurs is configured to deliver the same or similar precursors for the carbon-containing layer(s). However, the layer(s) can be deposited with different precursors. The invention also provides processing regimes that generate the treatment plasma and systems which use the treatment plasma. The carbon-containing material can be used in a variety of layers, such as barrier layers, etch stops, ARCs, passivation layers, and dielectric layers.